The broad objectives of the proposed research are to develop and apply methods for the determination of the molecular structure of peptides and proteins in solution. The ultimate aims of this work include the understanding of a. certain protein structure: function relationships, b. some of the mechanisms of cation transport through membranes, and c. the nature and spatial relationships of certain membrane proteins. A major effort will be the use of circular dichroism spectroscopy for the determination of cyclic peptide conformations in solutions and in lipid bilayers. The cation binding constants of some synthetic cyclic peptides will be determined through the use of circular dichroism. Using a variety of cyclic peptides, we hope to obtain information on the structurally essential determinants which make for strong ion binding. A second major effort will be the determinaton of the conformations of peptides and proteins in model membrane systems using the techniques of circular dichroism (in conjunction with other spectroscopic methods). Oligopeptides will be examined in hydrophobic environments (hydrocarbon solutions and phospholipid vesicles). Such peptides will be used as models for complex membrane proteins which are located within the hydrophobic portion of the phospholipid bilayer of biological membranes.